The invention relates to improvements in hydraulically operated automatic transmission assemblies, and to a method of supplying hydraulic fluid to the fluid-consuming or utilizing constituents of such transmission assemblies.
German patent No. 195 46 293 A1 discloses a hydraulically operated automatic transmission assembly which can be utilized in the power train of a motor vehicle to transmit torque between the engine and the wheels, normally in response to engagement of a friction clutch which serves to transmit torque between the rotary output element of the engine and the rotary input element of the variable speed or change speed transmission forming part of the automatic transmission assembly. The patented transmission assembly employs at least one static fluid consumer, a hydraulic transmission regulating component (e.g., a proportional and/or another valve), and at least one dynamic fluid consumer which is controlled by the transmission regulating component(s). The at least one static fluid consumer can include or constitute a fluid cooling unit, and the at least one dynamic fluid consumer can constitute a regulating arrangement for a continuously variable transmission (CVT). The speed ratio of such CVT is variable by the at least one transmission regulating component of the hydraulic transmission regulating unit. The patented transmission assembly further comprises a hydraulic resistor which is installed in a conduit serving to supply pressurized hydraulic fluid from the source to the static and dynamic fluid consumers. The source can include a pump which circulates transmission fluid in the automatic transmission assembly.
The aforementioned conduit receives hydraulic fluid from a fluid conveying unit which supplies fluid for the CVT and is located upstream of a volumetric flow regulator the regulating or adjusting function of which is influenced by the hydraulic resistor. In other words, the hydraulic resistor determines or controls the maximal volumetric flow of the working fluid because the quantity of conveyed fluid depends upon the RPM of the fluid conveying unit. Thus, when the RPM rises to a predetermined value, the fluid conveying unit delivers a volumetric flow of the working fluid which exceeds the fluid requirements of the automatic transmission assembly. The total or overall fluid flow which is supplied by the fluid conveying unit is divided into first and second flows for the static and dynamic fluid consumers, respectively.
As used herein, the term xe2x80x9cdynamic fluid consumerxe2x80x9d is intended to denote each consumer which, at least for a certain relatively short interval of time, requires a varying supply of hydraulic fluid. For example, an actuator in the hydraulic circuit of a prime mover is operated by receiving a variable supply of hydraulic fluid. In addition to the aforediscussed variable-RPM consumers (such as a CVT), dynamic fluid consumers further encompass, for example, various types of engageable and disengageable clutches including the so-called lockup or bypass clutches of torque converters. On the other hand, the term xe2x80x9cstatic fluid consumerxe2x80x9d is intended to denote those consumers of hydraulic fluid which, at least as a rule, receive fluid at a constant or substantially constant rate. Such static fluid consumers include cooling units for hydraulic fluid, the torque converter(s) and the lubricating means.
The patented automatic transmission assembly is operated in such a way that the conduit conveys the regulated volumetric flow into the transmission regulating unit. A portion of such flow is lost in the dynamic fluid consumers and as a result of leakage. The remainder of the flow is conveyed into the static fluid consumer or consumers. Any fluid that remains is caused to enter the suction side of the fluid conveying unit. The just described sequence of utilization of the fluid flow is considered to be necessary in order to ensure that a body of highly pressurized fluid reaches those consumers (normally or preferably including the dynamic consumer or consumers) which require a highly pressurized fluid, and that the working fluid thereupon reaches the low-pressure consumer or consumers normally encompassing the static fluid consumer(s). The fluid pressure is selected or regulated prior to admission into the consumer(s) requiring highly pressurized hydraulic fluid; however, the pressure of hydraulic fluid which is conveyed to the static fluid consumer(s) and/or to other consumers of lower-pressure fluid is normally determined by the quantity of fluid which is available for such purpose and by the geometry (a) of the piping which confines the low-pressure fluid and (b) the static fluid consumer(s). This results in the establishment, in the low-pressure region, of a specific xe2x80x9cbackwaterxe2x80x9d effect.
In an automatic transmission assembly for use in a motor vehicle, it is normally desirable or necessary to ensure that the operation be satisfactory while the temperature of transmission fluid fluctuates within a range of between about xe2x88x9230xc2x0 C. and +140xc2x0 C. When the fluid temperature (within the just mentioned range) is relatively high, the losses due to leakage increase (because the viscosity of the fluid is relatively high) well above average losses, and this applies especially for leakages in the transmission regulating unit. The fluid which escapes due to such increased temperature-induced reduction of viscosity is considered a lost fluid, i.e., a fluid which is not returned into the intake of the fluid conveying unit including the pump or another source of pressurized fluid.
It has been found that, if the temperature of the transmission fluid rises to a high or very high value (e.g., to a range of between +90xc2x0 C. and +140xc2x0 C.), the quantity of hydraulic fluid reaching the low pressure section (including the static fluid consumer or consumers) is too low. Thus, the operation of the lubricating system and/or of the cooling system of the automatic transmission assembly is likely to be unsatisfactory. Consequently, the temperature of fluid which has been caused to flow through the cooling unit or units is not sufficiently low (i.e., has not been sufficiently lowered) to ensure adequate cooling of the entire supply of transmission fluid because the percentage of fluid flowing through the cooling unit or units is too small. This entails a further rise of fluid temperature, i.e., a further drop of viscosity and additional leakage. Such chain reaction entails a progressively decreasing rate of fluid flow through the cooling system and a progressively increasing heating of the circulating transmission fluid. The result is an unstable condition of the automatic transmission assembly, and such condition is aggravated due to continuously increasing percentage of escaping leak fluid so that, if such situation persists, all consumers are likely to receive insufficient quantities of transmission fluid. Attempts to overcome such problems in presently known automatic transmission assemblies include an increase of the regulated volumetric flow.
If the temperature of the transmission fluid drops to a low or very low value (e.g., to between about xe2x88x9230xc2x0 C. and 0xc2x0 C.), the static fluid consumer or consumers receives or receive relatively large quantities of hydraulic fluid. Furthermore, as the viscosity of the transmission fluid increases, friction within the fluid also increases; this is particularly undesirable in connection with the flow of fluid through the conduits. Consequently, the pressure of fluid in the static consumer(s) is likely or bound to rise to an excessive value, namely to a value which can entail a destruction of a static fluid consumer (e.g., the fluid cooling unit or units). Moreover, the high pressure of fluid entering the low-pressure fluid consumer or consumers is bound to exert an adverse influence upon (such as an excessive rise of pressure of) fluid flowing in the dynamic consumer or consumers as well as of fluid flowing back into the fluid conveying or supplying unit. This can cause extensive damage to such constituents of the automatic transmission assembly and a pronounced drop of the efficiency of such assembly.
Another drawback of the aforediscussed conventional automatic transmission assemblies is that, when the fluid requirements of the dynamic consumers are high or very high, the surplus over the normal or average fluid requirements of such dynamic consumer(s) is detracted from the fluid which is normally available for static fluid consumers and is no longer returned to the fluid conveying unit, i.e., to the pump. For example, the fluid requirements of dynamic fluid consumers are likely or bound to increase for relatively short periods of time during filling of clutches and/or during actuation of the speed ratio selector for the change-speed transmission (such as the aforementioned continuously variable transmission). Such losses of transmission fluid must be taken into consideration in connection with the calculation of those quantities of transmission fluid which are to be made available for the static fluid consumer(s).
This application claims the priority of the commonly owned copending German patent application Serial No. 199 30 989.2 filed Jul. 5, 1999. The disclosure of the just mentioned priority application, as well as the disclosure of each and every U.S. and/or foreign patent and/or patent application identified in the specification of the present application, is incorporated herein by reference.
An object of the invention is to provide a novel and improved method of supplying hydraulic fluid to the consumers in an automatic transmission assembly.
Another object of the invention is to provide a method which renders it possible to operate with relatively small quantities of transmission fluid or another suitable hydraulic fluid.
A further object of the instant invention is to provide a method which renders it possible to invariably satisfy or meet the requirements of the static fluid consumer(s) even if the requirements of the dynamic fluid consumer(s) fluctuate within a wide range.
An additional object of the present invention is to provide a method which ensures that pronounced changes or fluctuations of the temperature of transmission fluid cannot, or are less likely to, exert an adverse influence upon the availability of fluid for proper operation of one or more static and/or dynamic fluid consumers.
Still another object of the invention is to provide a novel and improved hydraulically operated automatic transmission assembly which can be utilized for the practice of the above outlined method.
A further object of the invention is to provide an automatic transmission assembly with novel and improved means for allotting requisite quantities of transmission fluid for use by the static and dynamic fluid consumers.
Another object of the invention is to provide a motor vehicle wherein the power train embodies a hydraulically operated automatic transmission assembly of the above outlined character.
An additional object of the invention is to provide an automatic transmission assembly with novel and improved means for rendering the quantities of transmission fluid which are available for one of the static and dynamic fluid consumers less dependent upon, or independent from, the fluid requirements of the other of the static and dynamic components.
Still another object of the invention is to provide a novel and improved array of hydraulic lines for use in the above outlined automatic transmission assembly.
A further object of the invention is to provide a novel and improved combination of valves, flow restrictors and other hydraulic fluid flow influencing components for use in the above outlined automatic transmission assembly.
Another object of the invention is to provide a novel and improved automatic transmission assembly which can be installed in existing power trains of motor vehicles as superior substitutes for heretofore known automatic transmission assemblies.
An additional object of the invention is to provide a novel and improved modular automatic transmission assembly which can be utilized in the power trains of motor vehicles.
One feature of the instant invention resides in the provision of a method of supplying hydraulic fluid (such as a transmission fluid) to at least one static consumer and at least one dynamic consumer. The consumers form part of an automatic transmission assembly, and the method comprises the steps of establishing a source of pressurized hydraulic fluid, supplying a first fluid flow from the source to the at least one dynamic consumer along at least one first path, and conveying a second fluid flow from the source to the at least one static consumer along at least one second path wherein the fluid is not influenced by the at least one dynamic consumer (such terminology embraces situations and/or circumstances when the fluid being supplied to the at least one static consumer is not appreciably influenced by the at least one dynamic consumer).
The method can further comprise the step of regulating the rate of fluid flow (i.e., the volumetric flow) of fluid along the second path. Such regulating step can include controlling the pressure of fluid flow along the second path, e.g., maintaining the pressure of fluid in the second path below a predetermined maximum value, preferably within a predetermined range.
The method can also comprise the step of regulating the rate of fluid flow along the first path.
Furthermore, the improved method can comprise the steps of conveying a third fluid flow or stream from the source (such as a vane pump) along a third path, diverting a portion of the third flow from the third path into the at least one first path to thus form the first flow or stream, and diverting or directing a second portion of the third flow from the third path into the at least one second path to thus form the second flow or stream.
Morover, the improved method can comprise the step of propagating the first and second fluid flows along the respective paths independently of each other.
The flow of fluid to the consumers can be controlled by a flow regulating unit having at least one transmission regulating component (such as a valve), and the fluid supplying step of such method can include influencing the first fluid flow by the at least one regulating component of the regulating unit.
Numerous embodiments of novel and improved apparatus which can be utilized for the practice of the above outlined method will be described hereinbelow. One such (hydraulically operated) apparatus (hereinafter called automatic transmission assembly or assembly or transmission assembly for short), which is especially suited for utilization in the power train or drive train of a motor vehicle, comprises at least one static fluid consumer, at least one dynamic fluid consumer, a regulating unit including at least one transmission regulating component, a source of pressurized hydraulic fluid, means for supplying a first stream or flow of pressurized fluid from the source to the at least one dynamic consumer along a first path wherein the first flow is influenced by the at least one regulating component, and means for conveying a second flow or stream of pressurized fluid from the source to the at least one static consumer along a second path wherein the fluid is not influenced by the at least one dynamic consumer.
Another embodiment of the improved hydraulically operated transmission assembly comprises at least one static fluid consumer, at least one dynamic fluid consumer, a source of pressurized hydraulic fluid, a fluid-supplying first conduit connecting the outlet of the source with the at least one static fluid consumer, a volumetric flow regulator in the first conduit, means for influencing the flow regulator (such influencing means includes a hydraulic resistor in the first conduit), a second conduit which receives fluid from the first conduit upstream of the hydraulic resistor and is connected to the at least one dynamic fluid consumer, and a transmission regulating unit including at least one component (such as a 4/2-way valve or a pressure raising valve) arranged to regulate the flow of fluid in the second conduit.
The second conduit can branch off the first conduit upstream of the volumetric flow regulator.
The aforementioned means for influencing the flow regulator can be installed in the first conduit downstream of the flow regulator, and the second conduit can branch off the first conduit downstream of the volumetric flow regulator but upstream of the influencing means.
The improved assembly can further comprise a fluid conveying unit having a housing for the source, and the aforementioned hydraulic resistor can be disposed in such housing. The housing of the fluid conveying unit can accommodate the source and the hydraulic resistor, the source and the volumetric flow regulator, or the source jointly with the hydraulic resistor and the flow regulator.
The hydraulic resistor can be installed in the transmission regulating unit, and the assembly can further comprise at least one additional conduit which serves to return fluid from the hydraulic resistor to the volumetric flow regulator.
The source of pressurized fluid can form part of the fluid conveying unit, and the hydraulic resistor and/or the volumetric flow regulator can be installed in the first conduit between the source and the transmission regulating unit.
The volumetric flow regulator can be installed in the transmission regulating unit.
The aforementioned housing of the fluid conveying unit can be designed to accommodate the source and can be affixed to the transmission regulating unit.
The transmission regulating unit can comprise a plurality of components which serve to regulate the flow of fluid in the second conduit, and the first conduit can include a section which connects one of the plurality of components with the at least one static fluid consumer; the hydraulic resistor can be disposed in the aforementioned section of the first conduit.
The volumetric flow regulator can comprise a valve having a body defining a chamber for a reciprocable valving element. Such assembly can further comprise a first return conduit having an intake end communicating with the first conduit upstream of the hydraulic resistor and a discharge end communicating with the chamber at a first end face of the valving element, and a second return conduit having an inlet communicating with the first conduit downstream of the hydraulic resistor and an outlet communicating with the chamber at a second end face of the valving element.
The hydraulic resistor can comprise a measuring diaphragm and/or a measuring throttle.
It is also possible to design the improved assembly in such a way that the inlet of a return conduit communicates with the first conduit downstream of the hydraulic resistor and that the outlet of such return conduit discharges fluid into the aforementioned volumetric flow regulator. The return conduit can contain a damping diaphragm.
The volumetric flow regulator can be installed in the fluid flow conveying unit, the same as the source of pressurized fluid, and the hydraulic resistor can be installed in the transmission regulating unit.
If the source, the hydraulic resistor and the flow regulator are installed in the housing of the fluid conveying unit, a first portion of the first conduit in such assembly can be disposed in the fluid conveying unit and a second portion of the first conduit is connected to the at least one static consumer. A first portion of the second conduit can be disposed in the fluid conveying unit and a second portion of such second conduit is connected to the at least one dynamic consumer.
The dynamic fluid consumer or consumers can include a transmission (such as a planetary or a CVT) and/or a friction clutch, and the static fluid consumer or consumers can include at least one fluid cooling unit and/or a torque converter and/or at least one further consumer (such as a lubricating unit).
If the at least one dynamic consumer comprises a CVT, the assembly can further comprise a torque sensor which is connected with the output of a prime mover (such as the internal combustion engine of a motor vehicle) and is associated with the CVT. The latter can be of the type embodying first and second adjustable pulleys, an endess flexible element (such as a link chain) trained over the pulleys and hydraulic fluid-operated adjusting motors for the pulleys. Such motors can constitute dynamic fluid consumers.
It will be seen that, if the transmission regulating unit comprises or controls a hydraulically adjustable CVT, the dynamic fluid consumer means can comprise hydraulic adjusting means (such as the aforementioned motors) for the CVT.
In a further embodiment of the improved adjustable transmission assembly, the hydraulic resistor is variable in depedency upon temperature changes of the hydraulic fluid. Such hydraulic resistor can comprise a measuring throttle. The arrangement can be such that the hydraulic resistor defines a path for the flow of hydraulic fluid from the outlet of the source of pressurized fluid to the at least one static fluid consumer, and the path for the flow of fluid through the resistor is variable as a function of temperature changes of conveyed fluid.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved hydraulically operated automatic transmission assembly itself, however, both as to its construction and the modes of assembling and operating the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.